永磁变刚度机构柔性机器人力学特性研究

摘要

提出了一种柔性机器人用永磁变刚度机构.由于电动机转矩有限,在不用增加绳索拉力的情况下,通过该机构实现了柔性机器人关节更强的变刚度能力.该永磁变刚度机构主要由磁弹簧单元和滑轮绳索单元构成.通过虚位移法建立了弹簧磁力和绳索拉力解析模型,通过实验对永磁体间磁力和绳索上的拉力进行测量,测量结果和模型计算结果基本吻合.其结果表明,永磁体间磁力、绳索拉力和刚度随永磁体间气隙减小呈非线性增加,随永磁体长度和平均半径的增加而增加,保持三角形结构高不变,绳索拉力和刚度随着三角形结构底长的增加而增加,减小滑轮半径,可以进一步增加绳索刚度变化范围.%A variable-stiffness mechanism using permanent magnet spring was proposed for elastic robots.Due to the motor torque limit,in the case of no increasing in wire tension,strong variable-stiffness was achieved.The permanent magnet variable stiffness mechanism was mainly composed of permanent magnetic spring structure and wire-driven system.The permanent magnetic spring structure was composed of a pair of annular permanent magnets which were arranged in coaxial and the same permanent poles were opposite.The wire-driven system was composed of a movable pulley and two fixed pulleys.The magnetic force of permanent magnetic spring and wire tension of wire-driven system mathematical models were established by virtual displacement method.The magnetic force and wire tension were also measured by experiment.The results of experimental measurement were in good agreement with the calculated results.The calculated and experiment results together showed that the magnetic force,wire tension and stiffness were increased nonlinearly with the decrease of air gap between the permanent magnets,and increased with the increase of axial length and average radius of the permanent magnet.The height of triangle structure of wire-driven system was kept constant,the wire tension and stiffness were increased nonlinearly with the increase of the triangle structure bottom of wire-driven system.Decreasing the radius of the pulley can further increase the range of the wire stiffness.